Temperature control is a very useful device for the public palace. BY using this technique it is possible to control thespeed of the fan automatically. It is possible to convert normal fan into temperature sensitive fan by adding a temperature sensitive logic. By using this technique we not only save the valuable energy but provide a smart automation logic in electrical systems.

IN normal temperature controller we get a output for on and off purpose only but in this project we control the speed of the fan automatically. In brief firstly we convert the temperature into small voltage with the help of lm 35 sensor. LM 35 is temerature sensor convert the temperature in to small voltage at very accurately. Output of the temperature sensor is further converted into digital signal with the help of the ADC. IN this project we use ADC0809 . ADC 0809 is a 8 bit ADC and convert the any analogue signal into digital signal in 100 microsecond. To control the ADC we required a clock pulse, and 4 different signal . All this signal is provided by the controller. IN this project we use ic 89s51 as a main controller. IC 89s51 sense the output from the ADC in hex code. This HEX code is further converted into binary code with the help of program code inside the controller. IN the output device we use LCD display . LCD display display the contents of the display with the help of the ASCII code. ASCII CODE is a special code for displaying the character in the LCD. In the controller we convert the binary code in to ASCII codes with the help of the code conversion program. Temperature sensor by the lm 35 is now display in the ASCII code on the LCD display.

In the controller. We take four different output from the controller. These different output display the different temperature zone step by step.

If the temperature is in between 25 to 30 then zone one is on and if the temperature is in between 30 to 35 then second zone is on. As the temperature increases different zones are on step by one. As the temperature zone increase. LCD display a speed 1 or 2,or3 on the second line of the display.

All the four zone are connected to the one variable resistor logic or connected to the fan regulator circuit.

We use main resistance of the fan regulator . In the normal fan regulator there is total 5 point for 5 different speed. We use the same resistance for control the speed of the fan or control the intensisty of the light.

What is the primary difference between a microprocessor and a micro controller?

Unlike the microprocessor, the micro controller can be considered to be a true “Computer on a chip”.
In addition to the various features like the ALU, PC, SP and registers found on a microprocessor, the micro controller also incorporates features like the ROM, RAM, Ports, timers, clock circuits, counters, reset functions etc.
While the microprocessor is more a general-purpose device, used for read, write and calculations on data, the micro controller, in addition to the above functions also controls the environment. 8051 micro controller

The 8051

The 8051 developed and launched in the early 80`s, is one of the most popular micro controller in use today. It has a reasonably large amount of built in ROM and RAM. In addition it has the ability to access external memory.

The generic term `8×51` is used to define the device. The value of x defining the kind of ROM, i.e. x=0, indicates none, x=3, indicates mask ROM, x=7, indicates EPROM and x=9 indicates EEPROM or Flash.

A note on ROM

The early 8051, namely the 8031 was designed without any ROM. This device could run only with external memory connected to it. Subsequent developments lead to the development of the PROM or the programmable ROM. This type had the disadvantage of being highly unreliable.

The next in line, was the EPROM or Erasable Programmable ROM. These devices used ultraviolet light erasable memory cells. Thus a program could be loaded, tested and erased using ultra violet rays. A new program could then be loaded again.

An improved EPROM was the EEPROM or the electrically erasable PROM. This does not require ultra violet rays, and memory can be cleared using circuits within the chip itself.

Finally there is the FLASH, which is an improvement over the EEPROM. While the terms EEPROM and flash are sometimes used interchangeably, the difference lies in the fact that flash erases the complete memory at one stroke, and not act on the individual cells. This results in reducing the time for erasure.

Different microcontrollers in market.

PIC One of the famous microcontrollers used in the industries. It is based on RISC Architecture which makes the microcontroller process faster than other microcontroller.

INTEL These are the first to manufacture microcontrollers. These are not as sophisticated other microcontrollers but still the easiest one to learn.

Atmel Atmel’s AVR microcontrollers are one of the most powerful in the embedded industry. This is the only microcontroller having 1kb of ram even the entry stage. But it is unfortunate that in India we are unable to find this kind of microcontroller.

Intel 8051

Intel 8051 is CISC architecture which is easy to program in assembly language and also has a good support for High level languages.

The memory of the microcontroller can be extended up to 64k.

This microcontroller is one of the easiest microcontrollers to learn.

The 8051 microcontroller is in the field for more than 20 years. There are lots of books and study materials are readily available for 8051.

Derivatives

The best thing done by Intel is to give the designs of the 8051 microcontroller to everyone. So it is not the fact that Intel is the only manufacture for the 8051 there more than 20 manufactures, with each of minimum 20 models. Literally there are hundreds of models of 8051 microcontroller available in market to choose. Some of the major manufactures of 8051 are

Ø Atmel

Ø Philips

Philips

The Philips‘s 8051 derivatives has more number of features than in any microcontroller. The costs of the Philips microcontrollers are higher than the Atmel’s which makes us to choose Atmel more often than Philips

Dallas

Dallas has made many revolutions in the semiconductor market. Dallas’s 8051 derivative is the fastest one in the market. It works 3 times as fast as a 8051 can process. But we are unable to get more in India.

Atmel

These people were the one to master the flash devices. They are the cheapest microcontroller available in the market. Atmel’s even introduced a 20pin variant of 8051 named 2051. The Atmel’s 8051 derivatives can be got in India less than 70 rupees. There are lots of cheap programmers available in India for Atmel. So it is always good for students to stick with 8051 when you learn a new microcontroller.